Finally worked it all out. Those buttons are tricky for a while. Now running Witcher 3 very smoothly through the display port at 21;9 3440 x 1440 and 95 refresh rate.
100 was flickery but 95 smooth - so there I be. Thank you again for your help.
With a 980 Ti you might be able to get a good frame rate at 3440x1440 so feel free to experiment. I only have a 970 so running at 3440 is pushing it for a 2015 game.
I'd recommend using a DisplayPort cable if you can get one, I believe that HDMI has a maximum of 50 FPS while DisplayPort will get 60 right away just from switching the cable and possibly more if you overclock with your monitor.
If you've got the annoying black bars out of the way and the HUD where you like it then you're good to go, enjoy your Ultrawide Witcher. Cheers!